I cannot get my Apple Watch to pair with my phone
Why won’t my Apple Watch pair with my phone?
Apple Watch Series 3, watchOS 7
Apple Watch Series 3 will only pair with an iPhone 6s or later running iOS 13 or later. If you have an older phone or an older version of iOS then it won't pair.
Source of requirements: https://support.apple.com/kb/sp766?locale=en_GB (near bottom of the page)
